Advances in polymerization and catalysis have resulted in the capability to produce many new polymers having improved physical and chemical properties useful in a wide variety of superior products and applications. With the development of new catalysts the choice of polymerization (solution, slurry, high pressure or gas phase) for producing a particular polymer has been greatly expanded. Also, advances in polymerization technology have provided more efficient, highly productive and economically enhanced processes. Especially illustrative of these advances is the development of technology utilizing bulky ligand metallocene catalyst systems and other advanced metallocene-type catalyst systems.
To utilize these systems in industrial slurry or gas phases processes, it is useful that the catalyst compound be immobilized on a carrier or support such as, for example silica or alumina. The use of supported or heterogeneous catalysts increases process efficiencies by assuring that the forming polymeric particles achieve a shape and density that improves reactor operability and ease of handling. However, bulky ligand metallocene and metallocene-type catalysts typically exhibit lower activity when supported than when utilized in unsupported or homogeneous form. This “support effect” makes commercialization of these promising catalyst systems more difficult.
U.S. Pat. Nos. 5,317,036 and 5,693,727 and European publication EP-A-0 593 083 and PCT publication WO 97/46599 all describe various processes and techniques for introducing liquid unsupported catalysts to a polymerization reactor.
U.S. Pat. No. 6,069,213 discloses combining a supported and an unsupported metallocene catalysts in the polymerization of olefins, European publication EP 0 965 601A disclose a combination of a solid Ziegler-Natta catalyst with a liquid catalyst in toluene or Kaydol activated with methyl alumoxane or modified methyl alumoxane, and Chinese Published Patent Application No. 97116451.7 discloses combining an unsupported metallocene with a supported methylalumoxane. None of these references, however, discloses a catalyst composition prepared by continuously combining a catalyst component slurry with a catalyst component solution, then introducing the combination into an operating polymerization reactor.
While all these methods have been described in the art, there exists a need to reduce the support effect for bulky ligand metallocene and metallocene-type polymerization catalyst compositions, for an improved method for introducing catalyst compositions, and especially for introducing mixed catalyst compositions, into a polymerization reactors, and for methods to control the properties of polymer products utilizing such catalyst compositions.